Most image projection systems consist of a projector and a flat screen. The projector produces an image through still slides, moving film or video. The flat screen receives the projected light and provides viewers with a planar image that is viewable from either one or both sides of the screen. One drawback associated with conventional projection systems that project onto a flat screen is that the picture is best viewed when the viewer's line of sight is precisely normal to the plane of the picture. In such systems, special consideration must be given to the positioning of the display within its environment because, typically, conventional projection systems, such as those used in movie theaters, cannot be viewed from the rear or extreme sides. Thus, the area within which a viewing audience can be accommodated is limited to locations with suitable sight lines. This ideal condition is difficult to realize when several people wish to view the picture simultaneously from varied locations.
Sometimes multiple flat screens are used in conjunction with each other to partially surround an audience with imagery, or to place imagery in the center of a theatre which can be viewed from multiple sides. What all these systems have in common is that the screen itself provides a static framework onto which a still or moving image is projected. Any movement or dynamism is provided exclusively by the medium which is projected; the environment for the projected light is always static, and the view of any one screen is optimal for only a relatively narrow angular displacement from the center of that screen.
In an attempt to overcome the viewing limitations associated with conventional projection systems, the present invention can provide up to a 360° viewing system including a shaped, revolving screen. Projecting an image on a shaped, revolving screen presents several problems that will be apparent to those of skill in the art. First, the shape of the image surface (the screen) is not flat, but rather is contoured. Second, the screen is not static, it is dynamic in its rotation around a center axis. The varying shape of the screen, the screen's movement, its resultant cone of projection, and the screen's angular displacement from the projection device create a constantly changing area of projection. The problem is twofold. First, glare from the projection source is apparent to a viewer standing on the opposite side of the rotating screen around one or more of its edges as it moves. Second, the resultant spill-light of portions of the image that miss the screen as it rotates fall upon the background surface of the theatre, its ceiling or floor surfaces, creating distracting patterns of light.
Additionally, when the projection axis of the system is not perpendicular to the viewing screen, a portion of the projected image may appear distorted (e.g., stretched or compressed). This distortion is commonly known as keystone distortion. For example, if the projector is situated above a line normal to the viewing area of the screen, then the image must be projected downward to the screen. As a result, the upper portion of the image may appear expanded or stretched in relation to the lower potion of the image, or the lower portion may appear condensed or contracted compared to the upper portion. The projected image may thus take on a trapezoidal or keystone shape. Depending upon the resolution or detail of the image being projected, the distortion may significantly degrade one's appreciation of the image. The present invention addresses these and other needs.